Immune mechanisms involving either trapping of circulating immune complexes by the glomerulus or the direct reaction of antibody with antigens in or of the glomerulus to be responsible for most instances of glomerulonephritis in man. The work on this project is designed to better define and understand these mechanisms and the role of similar mechanisms in the production of tubulo-interstitial nephritis. Renal and serum specimens from nephritic individuals are submitted for immunopathologic study to define the immune processes as fully as possible in each individual. More refined techniques to identify mechanisms of injury are being developed or evaluated. Current interest centers around serologic tests for detecting circulating immune complexes or antiglomerular basement membrane antibodies. When fully evaluated, these tests should become useful clinical tools. The search for nephritogenic immune mechanisms is extended to relevant animal models of renal injury. The combined use of human studies and animal modeling provides an ideal environment for extension of our knowldege in this significant area of health care.